The Harderian gland is a major lacrimal gland found in all animals with a nictitating membrane. The gland contains two major cell populations, a tubular secretory epithelium which secretes a serous fluid and lymphoid tissue consisting primarily of B-cells which secrete IgA. The gland is densely innervated and our preliminary data show that noradrenalin (NA) containing fibers are present as well as substance P-like, VIP-like and eukephalin-like immunoreactivity. Further these anatomical studies show that NA fibers are morphologically closer to the B-cells ihan to other cell types. Since there is some evidence for neuronal modulation of antibody production in spleen we will test this hypothesis in Harderian gland where antibody production in the tears can be measured. We will use immunocytochemical techniques at the light and electron microscope levels to determine the details of the innervation pattern. We will examine the pattern in chicks at different ages as the full complement of B-cells is not found until about 1 month before hatching. We will collect tears of normal and stimulated birds to see if antibody production is regulated as is secretion of the serous fluid.